Hollow stoker grate



Dec. 26, 1961 E. R. MITCHELL ET AL 3,014,439

HOLLOW STOKER GRATE Filed July 11, 1960 2 TORS/ Midi United States Patent one 3,014,439 Patented Dec. 26, 1961 3,014,439 HOLLOW STOKER GRATE Earland R. Mitcheii and Frank D. Friedrich, Gttawa,

Ontario, Canada, assignors to Her Majesty the Queen in right of Canada as represented by the Minister of Mines and Technicai Surveys Fiied July 11, 19st Ser. No. 42,077 Claims. (Cl. 11074) This invention relates to sto-ker grate of the general type disclosed in our copending application Serial No. 853.802, filed November 18, 1959.

The grate disclosed in such copending application included the provision of a particular arrangement of combustion air openings in the burning surface of the grate whereby a more satisfactory and eflicient combustion of coals, especially of the low ash fusion type, may take place. I

it is an object of this invention to provide a grate composed of a plurality of composite hollow grate bars of simple and convenient construction and wherein an extended circulation of combustion air may take place for pro-heating of such air whereby a more eflicient operation of the grate occurs.

The invention will be described with reference to the accompanying drawing, in which- FIGURE 1 is a partial plan View of a grate in accordance with the invention,

FIGURE 2 is a side elevation of the grate showing a stationary grate bar,

FIGURE 3 is a partial side elevation of the grate showing a moving grate bar,

FIGURE 4 is an inner side elevation of a grate bar section,

FIGURE 5 is a cross-section on line 5-5 of FIGURE 2, and

FIGURE 6 FIGURE 2.

In the drawing, 1 designates generally the grate of the present invention as mounted on walls 2 and 3 of a conventional furnace having a rocking bar 4 mounted on a supporting wall 5 which defines a main air chamber 6.

The grate comprises a plurality of grate bars 7 each composed of two similar half sections 8- and 9. As is conventional, each grate bar has a nose Portion 10, an intermediate portion 11, and a tail portion 12.

Each section 8 and 9 comprises a substructure web or side wall 13 (which in the operative position of the grate is normally disposed in vertical or upright position) and a top fuel-receiving surface 14 defined by the upper edge of wall '13, an outer flange 14a projecting laterally from the outer surface of wall 13 and an inner flange 1o projecting laterally from the inner surface of wall 13. Each sect-ion 8 and 9 also has an outer flange 16 extending along the bottom edge of the wall 13 in the nose portion thereof and inner and outer flanges 17 and 13 extending along the bottom edge of the wall 13 in the tail portion thereof, the bottom edge of the wall 13 in the intermediate portion thereof being unflanged.

The extreme end of each nose portion is inwardly thickened at 19 and the extreme end of each tail portion 12 is inwardly thickened at 20, the inner flange terminating at such thickened areas and the inner flange 17 of the tail portion terminating at the thickened area 20.

Preferably, as shown, the flange 15 of section 8 i recessed at 21 from end to end thereof and the flange 15 of section 9 is provided with a rib 22 extending from end to end thereof arranged to fit into the recess 21 when the sections are placed in laterally abutting relation. In such relation, the inner flanges 15 and 17 and the thickened areas 19 and 2t? of the two sections 8 and 9 are in coextensive engagement with each other.

is a cross-section on line 66 of Each section 8 and has on the inner surface of wall 13 a longitudinally extending groove 23 which may be formed by spaced ribs 24, such groove extending from the flange 15 in the nose portion throughout the major extent of intermediate portion 11 to a point closely adjacent but spaced from the tail portion 12. Preferably such groove is slightly downwardly inclined whereby it is of gradually increased distance from the flange 15 in the intermediate portion thereof from the nose towards the tail portion. Each section 8 and 9 also has on the inner surface of wall 13 a longitudinally extending groove 25, which may be formed by spaced ribs 26, such groove extending throughout the intermediate portion 11 and being located substantially parallel to and closely adjacent the bottom edge of wall 13.

The laterally aligned grooves 23 of sections 8 and 9 support a plate 27 and the laterally aligned grooves 25 support a plate 28 (in the abutting relation of sections 8 and 9). The sections 8 and 9 are bolted together in such abutting relation by bolts 29 extending through the thick ened areas 19 and 20.

Each section 8 and 9 has a plurality of openings 3t extending through the wall 13 in the area between plate 27 and the upper or top surface 14. Preferably, such openings are longitudinally aligned and at uniform distance from the plate 27 whereby they are of progressively greater distance from the top surface 14 in the direction from the nose portion towards the tail portion thereof. Preferably also, openings 3G in section 8 are laterally disaligned or offset with respect to openings 30 in section 9 for more effective distribution of air discharged therefrom. Moreover, as shown, the holes 30 in each grate bar section are spaced apart at gradually increased distance from the nose to the tail portion, i.e., the holes are closer to gether at the nose end than they are at the tail end of the bar.

The grate bars '7 may be alternately arranged for stationary positioning on walls 2 and 3 and for moving relation with respect to such Walls in conventional manner.

Thus, the sections 8 and 9 of each of the stationary series of bars are provided with abutting thickened areas 31 between the nose and intermediate portions of the lower edge thereof, such areas 31 having a curved lower surface 32 for sliding engagement by the lug 33 of the rocking bar 4. The nose portions of the sections have a notch 34 therein for reception of a flange 35 on the wall 2.

The sections 8 and 9 of each of the moving series of bars are provided with abutting thickened areas 36 between the nose and intermediate portions of the lower edge thereof, and a notch 37 in such areas 36 for reception of the lug 33 of the rocking bar, the nose portions of the sections having a flat lower surface 38 for sliding engagement by the lug 33 of the rocking bar.

It will be apparent, as shown in FIGURES 5 and 6, that the composite bar composed of the two attached sections 8 and 9 forms between such sections an air-receiving chamber 39 which is closed at the top by abutting flanges 15, at the ends by abutting thickened areas 19 and 2t and at the bottom by abutting thickened areas 31 or 36 and flanges 1'7, and by plate 28. Since the lower edges of the nose portions of Walls 13 are unflanged, an air inlet opening 49 is provided therebetween.

The plate 27 divides the air-receiving chamber 39 into a first or lower part 41 which communicates at one end (in the nose portion thereof) with air inlet 49 and at the other end (in the tail portion thereof) with a second or upper part 4 2 from which air may escape through openings 30. Thus, incoming air will first flow through the chamber part 41 of the bar from the nose to the tail portion thereof and will then reverse its flow in the tail portion and. flow through the chamber part 42 from the tail to the nose posit-ion. As the air flows through part 42 it is discharged through openings 30, such openings being positioned for most effective distribution of the air between adjacent grate bars.

Distribution of the air discharged from openings 30 over the fuel burning surfaces 14 of the grate may be effected in a manner now to be described.

Each outer flange 14a of each grate bar 7 is provided on its outer surface with a plurality of ribs 4-3 defining therebetween slots 44, the ribs 43 of one flange 14 being laterally disaligned with respect to those of the other flange 14 whereby the ribs of one grate bar will extend into the slots of adjacent grate bars. There is thus pro vided a plurality of air openings 45 in the fuel burning surfaces 14 of the grate, the arrangement of such openings being substantially as described in the aforementioned copending application.

In operation, the incoming air is subjected to an efiicient pre-heating step by reason of its confined circulation initially from the nose end to the tail end of the bar and its reverse flow from the tail end for distribution through openings 30. It will be observed that such openings 30 are located a substantial distance (and this may be of the order of 1% to 2% inches) below the hot fuel-burning surfaces 14 whereby they will not interfere with eflicient heat transfer from the grate surfaces 14 through the webs or walls 13. Moreover, it will be observed that the openings 30 are closer together and closer to the fuel burning surfaces 14 in the nose and adjoining area of the grate where the heat is normally greater.

We claim:

1. A grate bar having a nose portion, an intermediate portion, and a tail portion, and comprising a pair of laterally aligned half sections secured together, each said section comprising a longitudinally extending supporting web having a top edge and a bottom edge, each said supporting Web extending through said portions and forming enclosing side walls for said grate bar, said top edge having inner and outer flanges extending from end to end of said grate bar and forming a top fuel receiving surface, said inner flanges of said sections being in engagement with each other to space said webs apart and provide an air receiving chamber therebetween, a separate closure plate carried by said webs adjacent said bottom edges thereof and joining said bottom edges substantially throughout said intermediate portion to provide a bottom closure for said chamber, said chamber having an air inlet disposed between said bottom edges in said nose portion, said bottom edges in said tail portion having flanges closing said chamber in said tail portion, and a separate partition plate carried by and between said webs, said partition plate being disposed in said chamber between said top and bottom edges and dividing said chamber into upper and lower parts, said partition plate extending through said nose and intermediate portions and terminating inwardly of said tail portion to provide communication between said chamber parts in said tail portion, each said web having a series of air discharge openings leading from said chamber, and each said outer flange having air receiving slots in the edge surface thereof.

2. A grate bar having a nose portion, an intermediate portion, and a tail portion, and comprising a pair of laterally aligned half sections secured together, each said section comprising a longitudinally extending supporting web having a top edge and a bottom edge, each said supporting web extending through said portions and forming enclosing side Walls for said grate bar, said top edge having inner and outer flanges extending from end to end of said grate bar, and forming a top fuel receiving surface, said inner flanges of said sections being in engagement with each other to space said webs apart and provide an air receiving chamber therebetween, a longitudinally extending partition connecting said webs and disposed in said chamber between said top and bottom edges and dividing said chamber into upper and lower parts, said parts having communication with each other only adjacent one end of said chamber, and closure means joining said bottom edges of said sections throughout their major extent, said chamber having an air inlet disposed between said bottom edges, each said web having a series of air discharge openings in the area thereof forming said upper part of said chamber and leading from said upper part of said chamber, and each said outer flange having air receiving slots in the edge surface thereof.

3. A grate bar as defined in claim 2, said partition terminating inwardly of said tail portion to provide communication between said chamber parts in said tail portion.

4. A grate bar as defined in claim 2, said air discharge openings of each said series being arranged in a row extending longitudinally of said web and being spaced at gradually increased distances from said fuel receiving surface from said nose portion towards said tail portion.

5. A grate bar as defined in claim 4, said air discharge openings of one said series'being laterally disaligned with respect to said air discharge openings of the other of said series.

References Cited in the file of this patent UNITED STATES PATENTS 1,106,583 Read Aug. 11, 1914 1,435,948 Van Brunt Nov. 21, 1922 1,513,987 Hare Nov. 4, 1924 1,779,852 Parker Oct. 28, 1930 

